U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
To reach the tidal bench marks from the Dauphin Island Post Office, proceed 0.3
km (0.2 mi) south on Lockland Street to its intersection with Bienville
Boulevard, then 4.0 km (2.5 mi) east on Bienville Boulevard to Fort Gaines at
the east end of the island. The bench marks are located near Fort Gaines and
the Dauphin Island Sea Lab complex. The tide gage is located atop a 7.6 m (25
ft) high tower on the SE side of a large fishing pier north of the fort.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: NO 1 1960
DESIGNATION: 873 5180 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 787
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: BH1756
SETTING CLASSIFICATION: Gun mount on wall OPUS PID#: BH1756
LATITUDE: 30° 15.0' N ( 30.24958) LONGITUDE: 88° 4.5' W ( -88.07553)
The primary bench mark is set in the top of a concrete gun mount at the NE
corner of the mount located outside the main fort wall near the NW corner of the
main fort, 6.98 m (22.9 ft) west of the east edge of the gun emplacement, 3.85 m
(12.6 ft) north of the south edge of the gun emplacement, 0.41 m (1.4 ft) south
of the north edge of the gun emplacement, and 0.39 m (1.3 ft) east of the west
edge of gun emplacement.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5180 B 1976
DESIGNATION: 873 5180 B TIDAL
MONUMENTATION: Tidal Station disk VM#: 792
AGENCY: National Ocean Survey (NOS) IDB PID#: BH1755
SETTING CLASSIFICATION: Concrete monument OPUS PID#: BH1755
LATITUDE: 30° 15.0' N ( 30.24969) LONGITUDE: 88° 4.6' W ( -88.07600)
The bench mark is set in a concrete monument at the NE corner of a U-drive
entrance to the parking area of Fort Gaines, 48.91 m (160.47 ft) east of the
west driveway entrance, 16.39 m (53.77 ft) south of the centerline of the
boulevard, 4.67 m (15.32 ft) west of the approximate center of the east drive to
the fort, and 2.60 m (8.53 ft) north of the wood fence at front of parking lot.
BENCH MARK STAMPING: 5180 C 1976
DESIGNATION: 873 5180 C TIDAL
MONUMENTATION: Tidal Station disk VM#: 793
AGENCY: National Ocean Survey (NOS) IDB PID#: BH1752
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: 30° 15.0' N ( 30.24947) LONGITUDE: 88° 4.6' W ( -88.07681)
The bench mark is set in top and near the north edge of a 5.0 m (16.4 ft) x 6 m
(19.7 ft) concrete slab, 18.50 m (60.70 ft) SSW of the SE corner of the east
wing of the Administration Building, 14.60 m (47.90 ft) SSE of the north guy
anchor of a tower, 14.20 m (46.59 ft) NNW of the SE guy wire anchor, 3.67 m
(12.04 ft) north of the south edge of slab, 3.11 m (10.20 ft) west of the east
edge of slab, 3.04 m (9.97 ft) east of the west edge of slab, and 0.79 m (2.59
ft) south of the north edge of slab.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 5180 E 1976
DESIGNATION: 873 5180 E
MONUMENTATION: Tidal Station disk VM#: 795
AGENCY: National Ocean Survey (NOS) IDB PID#: BH1754
SETTING CLASSIFICATION: Foundation pad OPUS PID:
LATITUDE: 30° 15.0' N ( 30.24933) LONGITUDE: 88° 4.6' W ( -88.07700)
The bench mark is set on top at the NE corner of a concrete foundation of a very
long aluminum storage shed behind the Administration Building/Library, 38.95 m
(127.79 ft) east of the centerline of the driveway on the west side of the
Administration Building/Library, 30.85 NNW of the NE corner of the tech support
shop, 28.12 m (92.26 ft) SW of bench mark C 1976, 20.55 m (67.42 ft) SE of the
SW corner of the Dauphin Island Sea Lab Library, 14.44 m (47.38 ft) SSE of the
SE corner of the Library/Administration Building, and 6.10 m (20.01 ft) west of
the center of door to shed. Note - the storage shed covers the southern half
of the mark.
BENCH MARK STAMPING: 21D - 2E
DESIGNATION: 873 5180 21D - 2E
MONUMENTATION: Survey disk VM#: 13671
AGENCY: US Army Corps of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: Unspecified OPUS PID#:
LATITUDE: 30° 15.0' N ( 30.24969) LONGITUDE: 88° 4.6' W ( -88.07667)
The bench mark is located 17.20 m (56.43 ft) ENE of the NE corner of the Dauphin
Island Sea Lab Building, 10.51 m (34.48 ft) west of the western-most entrance to
historic Fort Gaines parking lot, and 10.51 m (34.48 ft) west of the
western-most entrance to historic Fort Gaines parking lot.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 21D - 2C
DESIGNATION: 873 5180 21D - 2C
MONUMENTATION: Survey disk VM#: 16581
AGENCY: US Army Corps of Engineers (USE) IDB PID#:
SETTING CLASSIFICATION: Gun mount OPUS PID:
LATITUDE: 30° 15.0' N ( 30.24967) LONGITUDE: 88° 4.5' W ( -88.07542)
The bench mark is set in top of the NE corner of a concrete gun mount, outside
the main fort wall near the NW corner of the Fort Gaines, 3.54 m (11.61 ft)
north of bench mark NO 1 1960, 1.78 m (5.84 ft) NE of the SW face of the gun
mount, 1.56 m (5.12 ft) south of the north face of the mount, 1.24 m (4.07 ft)
NW of the SE face of the mount, 1.00 m (3.28 ft) north of the south edge of fort
wall, 0.91 m (2.99 ft) east of the west edge of the fort wall, and 0.85 m (2.79
ft) south of the north edge of fort wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
T I D A L D A T U M S
Tidal datums at DAUPHIN ISLAND (TEMP) based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: June 2005 - November 2005
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8735180 DAUPHIN ISLAND, MOBILE BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.377
MEAN HIGH WATER MHW = 0.372
MEAN TIDE LEVEL MTL = 0.188
MEAN SEA LEVEL MSL = 0.180
North American Vertical Datum NAVD88 = 0.070
MEAN LOW WATER MLW = 0.004
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
NO 1 1960 5.410 5.038
5180 B 1976 2.674 2.302
5180 C 1976 2.668 2.296
5180 E 1976 2.612 2.240
21D - 2E 2.144 1.772
21D - 2C 5.276 4.904
Foot Notes:
Elevations for benchmarks 21D-2E, 5180 B 1976, and 5180 E 1976 are based on one
differential leveling connection and do not meet the quality control standards
of the NOS. Therefore, caution should be used when deriving elevations for these
marks.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8735181 PUBLICATION DATE: 03/09/2006
Name: DAUPHIN ISLAND (TEMP)
AL
NOAA Chart: 11378 Latitude: 30° 15.0' N ( 30.25000)
USGS Quad: FORT MORGAN NW Longitude: 88° 4.5' W ( -88.07500)
D E F I N I T I O N S
Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal
Datum Epoch. It pertains to local mean sea level and should not be confused
with the fixed datums of North American Vertical Datum of 1988 (NAVD88).
NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum
constraint adjustment of Canadian/Mexican/United States leveling observations.
Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as
the single initial constraint. NAVD88 replaces NGVD29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD29 was originally derived from a general
adjustment of the first-order leveling networks of the U.S. and Canada after
holding mean sea level observed at 26 long term tide stations as fixed.
Numerous local and wide-spread adjustments have been made since establishment in
1929. Bench mark elevations relative to NGVD29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to
local MSL and other tidal datums may not be consistent from one location to
another.
The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique
identifiers for bench marks in the tidal and geodetic databases, respectively.
Each bench mark in either database has a single, unique VM# and/or PID# assigned.
Where both VM# and PID# are indicated, both tidal and geodetic elevations are
available for the bench mark listed. The NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.
The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD88 elevations.
The NAVD88 elevation relationship shown in the table is derived from an average
of several bench mark elevations relative to tide station datum. As a result of
this averaging, NAVD88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD88 elevations listed for
each bench mark in the NGS database.